Compositions and methods for treating or preventing convulsions or seizures

ABSTRACT

The present invention relates to compositions comprising S-tofisopam substantially free of R-tofisopam, and methods for treating or preventing convulsions and/or seizures comprising administration of the composition to subjects in need of treatment therefor. Also provided are compositions and methods for treating or preventing convulsions and/or seizures comprising administering S-tofisopam substantially free of R-tofisopam with another anti-convulsant.

This application is a continuation of application Ser. No. 10/008,516,filed Nov. 8, 2001, now U.S. Pat. No. 6,649,607, which claims benefitfrom U.S. Provisional Application No. 60/292,026, filed May 18, 2001.

FIELD OF THE INVENTION

The present invention relates to compositions and methods for treatingor preventing convulsions or seizures.

BACKGROUND OF THE INVENTION

Tofisopam is1-(3,4-dimethoxy-phenyl)-4-methyl-5-ethyl-7,8-dimethoxy-5H-2,3-benzodiazepine,which can be represented by the formula:

Tofisopam (racemic mixture) has been marketed under the names Grandaxin®and Seriel® as an anxiolytic. Although tofisopam is a benzodiazepine, itdiffers structurally from the classical diazepam-like benzodiazepines inthat the nitrogen atoms in the ring structure are positioned at 2,3instead of 1,4. Despite the structural similarity between tofisopam andclassical 1,4-benzodiazepines, the difference in position of thenitrogen in the benzodiazepine ring confers pharmacological activity ontofisopam that is very different from classical benzodiazepines.

A synthesis of tofisopam is described in U.S. Pat. No. 3,736,315.Tofisopam has a chiral center at carbon C-5 and therefore has twoenantiomers. In addition, each enantiomer of tofisopam can exist in twostable conformations based on the two configurations that can be assumedby the nitrogen containing benzodiazepine ring.

The molecular structure and conformational properties of tofisopam havebeen determined by NMR, CD and x-ray crystallographic methods (Visy, J.and Simongi, M., Chirality 1:271–275 (1989)). The 2,3 diazepine ringexists in two kinds of boat conformation. In the major conformers, (+)Rand (−)S, the ethyl group attached to the center of asymmetry C-5 has aquasiequatorial orientation, while in the minor conformers, (−)R and(+)S, the ethyl group is positioned quasiaxially. Thus, racemictofisopam can exist as four molecular species, i.e., two enantiomerseach of which exists in two chiral conformations. The sign of opticalrotation is reversed upon inversion of the diazepine ring. In crystalform, tofisopam exists only as the major conformations, withlevorotatory tofisopam being of the (S) absolute configuration (Toth, G.et al., J. Heterocyclic Chem. 20:709–713 (1983); Fogassy, E. et al., In:Bio-Organic Heterocycles, Van der Plas, H. C., Ötvös, L., Simongi, M.,eds. Budapest Amsterdam: Akademia; Kiado-Elsevier, 229:233 (1984)).

The absolute configuration of an asymmetric drug molecule can haveprofound effects on the efficacy of the drug. Fogassy et al., statesthat an abstract by Petocz et al. from a 1980 meeting describespharmacological tests in mice which show different biological activityfor the stereoisomers of tofisopam, including the observation that theactivity of racemic tofisopam does not correspond with the sum of theactivities of its enantiomers (Fogassy, E. et al., supra). However,Fogassy et al. does not describe the biological assays of the specificresults achieved by Petocz et al. Furthermore, a search of the prior artyielded no such abstract by Petocz et al. Thus, there is currently noindication that Petocz et al. exists or relates to S-tofisopam and itsunexpected properties.

In addition the binding of tofisopam enantiomers to human serum albuminhas been reported to be stereoselective and affected by theinterconversion of conformations (Simonyi, M., and Fitos, I., BiochemPharmacology 32:1917–1920 (1983)).

Hungarian Patent No. 178516 describes an attempt to separate theenantiomers of tofisopam and observations relating to the administrationof the separated products in mice. However, the purity of the separatedproducts administered to the mice is not reported. Further, the absoluteconfiguration of the separated products is not reported, and none of thetests in mice measured the anti-convulsant activity of the separatedproducts.

There have been two reports that tofisopam exhibits anti-convulsantactivity in mice. In 1981, C. Ito alleged that tofisopam can inhibitconvulsions induced by tryptamine in mice (Ito, C., Tokyo Med. College39:369–384 (1981); hereinafter “Ito”). However, the convulsion data ofIto does not support this conclusion. The administration of tofisopamaccording to the tests described in Ito appeared to have no effect ondecreasing the incidence of convulsions in the mice (Table 6, Itosupra). Furthermore, Ito did not test the anti-convulsant activity ofS-tofisopam substantially free of R-tofisopam.

In 1986, Pellow et al. reported that the administration of 100 mg/kg oftofisopam reduced the number of mice having convulsions induced by thecompound Ro 5-4864 (Pellow, S. and File, S., Drug Dev. Res. 7:61–73(1986)). However, Pellow et al. also reported that all of the treatedmice still experienced myoclonic jerks. In contrast, Pellow et al.reported that 25–50 mg/kg tofisopam had proconvulsant activity in TuckNo. 1 mice when administered in combination with 3 mg/kg picrotoxin or30 mg/kg pentylenetetrazole. Pellow et al. also reported that a dose of10–50 mg/kg of tofisopam had no affect on the number or severity ofconvulsions in Tuck No. 1 mice that had been given 6 mg/kg ofpicrotoxin. Likewise, in Tuck No. 1 mice that were given 60 mg/kg ofpentylenetetrazole, a dose of 10–25 mg/kg of tofisopam was reported tohave no effect as an anti-convulsant. Pellow et al. did not test theanti-convulsant activity of S-tofisopam substantially free ofR-tofisopam.

Numerous other reports, some of which were published after 1986, statethat tofisopam has no anti-convulsant properties (Mennini et al., Arch.Pharmacol. 32:112–115 (1982); Saano, V., Med. Bio. 64:201–206 (1986);Petocz, L., Acta Pharm. Hung. 63:79–82 (1993); Szego, J. et al., ActaPharm. Hung. 63:91–98 (1993)). None of the studies tested theanti-convulsant activity of S-tofisopam substantially free of its (R)enantiomer.

Tofisopam has been reported to enhance the actions of benzodiazepineanti-convulsants but not phenytoin, sodium valproate or carbamazepine(Saano, V., Med. Biol. 64:201–206 (1986)). For example, the potentiationaction of tofisopam was reported to be effective with diazepam againstconvulsions (Briley, M. Br. J. Pharmacol. 82:300P (1984); Mennini, T.,Naugn-Schmiedeberg's Arch Pharmacol. 321:112–115 (1982)), and againsttremors (Saano, V., Pharmacol. Biochem. Behav. 17:367–369 (1982); Saano,V., Med. Biol. 61:49–53 (1983)). None of these potentiation studiesexamined the effects of either of the enantiomers of tofisopam on theanti-convulsant activity of diazepam or other anti-convulsants.

SUMMARY OF THE INVENTION

An object of this invention is to provide new compositions and methodsfor treating and preventing convulsions and seizures. The presentinvention provides a composition comprising a therapeutically effectiveamount of S-tofisopam substantially free of its (R) enantiomer, and apharmaceutically acceptable carrier. A composition comprising a prodrugor pharmaceutically acceptable salt of S-tofisopam substantially free ofR-tofisopam is also contemplated.

Preferably, the amount of S-tofisopam or pharmaceutically acceptablesalt thereof is 80% or more by weight of the total weight of tofisopam.More preferably, the amount of S-tofisopam or pharmaceuticallyacceptable salt thereof is 85% or more by weight of the total weight oftofisopam. More preferably, the amount of S-tofisopam orpharmaceutically acceptable salt thereof is 90% or more by weight of thetotal weight of tofisopam. More preferably, the amount of S-tofisopam orpharmaceutically acceptable salt thereof is 95% or more by weight of thetotal weight of tofisopam. Most preferably, the amount of S-tofisopam orpharmaceutically acceptable salt thereof is 99% or more by weight of thetotal weight of tofisopam. In one aspect of the invention, theconformation of the S-tofisopam is 80%(−) and 20%(+).

The present invention also provides compositions comprising S-tofisopamsubstantially free of its (R) enantiomer, and one or more otheranti-convulsants. According to one embodiment, the other anti-convulsantis selected from the group consisting of phenytoin, mephenytoin,ethotoin, phenobarbital, mephobarbital, primidone, carbamazepine,ethosuximide, methsuximide, phensuximide, valproic acid, trimethadione,paramethadione, phenacemide, acetazolamide, progabide, diazepam,lorazepam, clonazepam, clorazepate and nitrazepam. In one embodiment,the other anti-convulsant is a benzodiazepine. In one preferredembodiment, the other anti-convulsant is a 1,4-benzodiazepine. In yetanother preferred embodiment, the other anti-convulsant is diazepam,lorazepam, clonazepam, clorazepate or nitrazepam.

In one embodiment, the pharmaceutical composition is acontrolled-release pharmaceutical composition.

The present invention provides methods of treating convulsions orseizures comprising administering to a subject in need of treatmenttherefor, a therapeutically effective amount of S-tofisopamsubstantially free of R-tofisopam sufficient to alleviate theconvulsions or seizures. Another embodiment of the invention relates tomethods of preventing convulsions or seizures in a subject at risk fordeveloping convulsions or seizures comprising administering to thesubject a therapeutically effective amount of S-tofisopam substantiallyfree of its (R) enantiomer sufficient to prevent the convulsions orseizures. Administration of a prodrug or pharmaceutically acceptablesalt of S-tofisopam according to the methods of this invention is alsocontemplated.

In another embodiment of this invention, the subject in need oftreatment is suffering from convulsions or seizures caused by a disorderor condition selected from the group consisting of epilepsy, acquiredimmunodeficiency syndrome (AIDS), Parkinson's disease, Alzheimer'sdisease, other neurodegenerative disease including Huntington's chorea,schizophrenia, obsessive compulsive disorders, tinnitus, neuralgia,trigeminal neuralgia, amyotrophic lateral sclerosis (ALS), tics (e.g.,Gille de la Tourette's syndrome), post-traumatic epilepsy, alcohol use,alcohol withdrawal, intoxication or withdrawal from barbiturates, brainillness or injury, brain tumor, choking, drug abuse, electric shock,fever (especially in young children), head injury, heart disease, heatillness, high blood pressure, meningitis, poisoning, stroke, toxemia ofpregnancy, uremia related to kidney failure, venomous bites and stings,withdrawal from benzodiazepines, febrile convulsions, and afebrileinfantile convulsions. In one preferred embodiment, the subject issuffering from convulsions or seizures caused by epilepsy.

The present invention also provides methods of treating of preventingconvulsions or seizures comprising administering to a subject in need oftreatment therefor a therapeutically effective amount of S-tofisopam,prodrug or salt thereof, substantially free of R-tofisopam together orsequentially with one or more other anti-convulsants. The otheranti-convulsant can be selected from the group consisting of, but notlimited to, phenytoin, mephenytoin, ethotoin, phenobarbital,mephobarbital, primidone, carbamazepine, ethosuximide, methsuximide,phensuximide, valproic acid, trimethadione, paramethadione, phenacemide,acetazolamide, progabide, diazepam, lorazepam, clonazepam, clorazepateand nitrazepam. In one embodiment, the other anti-convulsant is abenzodiazepine. In one preferred embodiment, the other anti-convulsantis a 1,4-benzodiazepine. In yet another preferred embodiment, the otheranti-convulsant is diazepam, lorazepam, clonazepam, clorazepate ornitrazepam.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 graphically depicts the dose-dependent effect of tofisopam onpicrotoxin-induced seizures in male NSA mice.

FIG. 2 graphically depicts the dose-dependent effect of S-tofisopam onpicrotoxin-induced seizures in male NSA mice.

FIG. 3 graphically depicts the dose-dependent anti-convulsant effect ofracemic tofisopam on picrotoxin-induced seizures in male NSA mice.

FIG. 4 graphically depicts the dose-dependent anti-convulsant effect ofdiazepam on picrotoxin-induced seizures in male NSA mice.

FIG. 5 graphically depicts the anti-convulsant effect of R-tofisopam onpicrotoxin-induced seizures in male NSA mice.

FIG. 6 graphically depicts the dose-dependent anti-convulsant effect ofS-tofisopam on picrotoxin-induced seizures in male NSA mice.

DETAILED DESCRIPTION OF THE INVENTION

A composition according to this invention comprises S-tofisopamsubstantially free of its (R) enantiomer. The term “substantially freeof its (R) enantiomer” as used herein means that the compositioncomprises at least 80% or more by weight of S-tofisopam and 20% byweight or less of R-tofisopam in terms of total weight of tofisopam. Ina preferred embodiment, the composition comprises at least 85% or moreby weight of S-tofisopam and 15% by weight or less of R-tofisopam interms of total weight of tofisopam. In a more preferred embodiment, thecomposition comprises at least 90% or more by weight of S-tofisopam and10% by weight or less of R-tofisopam in terms of total weight oftofisopam. In yet a more preferred embodiment, the composition comprisesat least 95% or more by weight of S-tofisopam and 5% or less ofR-tofisopam in terms of total weight of tofisopam. In a most preferredembodiment, the composition comprises at least 99% or more by weight ofS-tofisopam and 1% or less of R-tofisopam in terms of total weight oftofisopam. In one embodiment, the confirmation of S-tofisopam is 80% (−)and 20% (+).

Tofisopam can be synthesized according to methods known in the art. Forexample, a method for synthesis is described in U.S. Pat. Nos. 3,736,315and 4,423,044, the disclosures of which are incorporated by reference.The (S) enantiomer of tofisopam can be obtained by the methods describedherein (Example 1 or 3).

The compositions of the present invention comprise S-tofisopam,substantially free of R-tofisopam, or a prodrug or a pharmaceuticallyacceptable salt thereof as the active ingredient, and can also contain apharmaceutically acceptable carrier and optionally other therapeuticingredients.

In one embodiment, the composition of the present invention comprisesS-tofisopam and one or more other anti-convulsants. The otheranti-convulsant can be, e.g., phenytoin, mephenytoin, ethotoin,phenobarbital, mephobarbital, primidone, carbamazepine, ethosuximide,methsuximide, phensuximide, valproic acid, trimethadione,paramethadione, phenacemide, acetazolamide, progabide, diazepam,lorazepam, clonazepam, clorazepate or nitrazepam. In another embodiment,the composition of this invention comprises S-tofisopam and abenzodiazepine. In yet another embodiment, the composition of thisinvention comprises S-tofisopam and a 1,4-benzodiazepine. In yet afurther embodiment, the composition of this invention comprisesS-tofisopam and an anti-convulsant selected from the group consisting ofdiazepam, lorazepam, clonazepam, clorazepate and nitrazepam.

Prodrugs according to this invention are inactive derivatives ofS-tofisopam that are metabolized in vivo into the active agent in thebody. Prodrugs useful according to this invention are those that havesubstantially the same or better therapeutic value than S-tofisopam intreating or preventing convulsions or seizures. For example, a prodruguseful according to this invention can improve the penetration of thedrug across biological membranes leading to improved drug absorption;prolong duration of the action of the drug, e.g., slow release of theparent drug from the prodrug and/or decrease first-pass metabolism ofthe drug; target the drug action; improve aqueous solubility andstability of the drug (e.g., intravenous preparations, eyedrops etc.);improve topical drug delivery (e.g., dermal and ocular drug delivery);improve the chemical and/or enzymatic stability of drugs (e.g.,peptides); or decrease side effects due to the drug. Methods for makingprodrugs are know in the art (e.g., Balant, L. P., Eur. J. Drug Metab.Pharmacokinet. 15:143–153 (1990); and Bundgaard, H., Drugs of the Future16:443–458 (1991); incorporated by reference herein).

The term “pharmaceutically acceptable salt” refers to salts preparedfrom pharmaceutically acceptable non-toxic acids including inorganicacids and organic acids. Since S-tofisopam is basic, salts can beprepared from pharmaceutically acceptable non-toxic acids includinginorganic and organic acids. Such acids include malic, acetic,benzene-sulfonic (besylate), benzoic, camphorsulfonic, citric,ethenesulfonic, fumaric, gluconic, glutamic, hydrobromic, hydrochloric,isethionic, lactic, maleic, malic, mandelic, methanesulfonic, mucic,nitric, pamoic, pantothenic, phosphoric, succinic, sulfuric, tartaric,p-toluenesulfonic acid and the like. Particularly preferred arehydrobromic, hydrochloric, maleic, phosphoric, and sulfuric acids.

The compositions according to this invention can be prepared for oral,rectal, or transdermal use, e.g., using a patch. Alternatively,compositions can be prepared for sublingual or parenteral administration(including subcutaneous, intramuscular, intrathecal and intravenousadministration). The most suitable route in any given case will dependon the nature and severity of the condition being treated. According toone preferred aspect of this invention, the route of administration isthe oral route. According to another preferred aspect of this invention,the route of administration is rectal, intramuscular, intranasal orintravenous. According to yet another preferred aspect of the invention,the route of administration is intraperitoneal or subcutaneous. Thecomposition can be presented in a unit dosage form and prepared by anyof the methods well-known in the art of pharmacy.

In practical use, S-tofisopam or prodrug or salt thereof, substantiallyfree of R-tofisopam, can be combined as the active ingredient inadmixture with a pharmaceutical carrier according to conventionalpharmaceutical compounding techniques. The carrier can take a widevariety of forms depending on the form of preparation desired foradministration, e.g., oral or parenteral administration (includingintravenous injections or infusions). For example, carriers according tothis invention include starches, sugars, microcrystalline cellulose,stabilizers, diluents, granulating agents, lubricants, binders, fillersand disintegrating agents. Compositions for oral dosage form can includeany of the usual pharmaceutical media, e.g., water, glycols, oils,alcohols, flavoring agents, preservatives, coloring agents and the likein the case of oral liquid preparations, e.g., suspensions, elixirs andsolutions; or aerosols.

The compositions of the present invention can also be formulated so asto provide slow or control led-release of the active ingredient thereinusing, e.g., hydropropylmethyl cellulose in varying proportions toprovide the desired release profile, other polymer matrices, gels,permeable membranes, osmotic systems, multilayer coatings,microparticles, liposomes and/or microspheres.

In general, a controlled-release preparation is a composition capable ofreleasing the active ingredient at the required rate to maintainconstant pharmacological activity for a desirable period of time. Suchdosage forms can provide a supply of a drug to the body during apredetermined period of time and thus maintain drug levels in thetherapeutic range for longer periods of time than other non-controlledformulations.

For example, U.S. Pat. No. 5,674,533 discloses controlled-releasecompositions in liquid dosage forms for the administration ofmoguisteine, a potent peripheral antitussive. U.S. Pat. No. 5,059,595describes the controlled-release of active agents by the use of agastro-resistant tablet for the therapy of organic mental disturbances.U.S. Pat. No.5,591,767 describes a liquid reservoir transdermal patchfor the controlled administration of ketorolac, a non-steroidalanti-inflammatory agent with potent analgesic properties. U.S. Pat. No.5,120,548 discloses a controlled-release drug delivery device comprisedof swellable polymers. U.S. Pat. No. 5,073,543 describescontrolled-release formulations containing a trophic factor entrapped bya ganglioside-liposome vehicle. U.S. Pat. No. 5,639,476 discloses astable solid controlled-release formulation having a coating derivedfrom an aqueous dispersion of a hydrophobic acrylic polymer. Thesepatents are incorporated herein by reference.

Biodegradable microparticles can be used in the controlled-releaseformulations of this invention. For example, U.S. Pat. No. 5,354,566discloses a controlled-release powder that contains the activeingredient. U.S. Pat. No. 5,733,566, describes the use of polymericmicroparticles that release antiparasitic compositions. These patentsare incorporated herein by reference.

The controlled-release of the active ingredient can be stimulated byvarious inducers, for example pH, temperature, enzymes, water, or otherphysiological conditions or compounds. Various mechanisms of drugrelease exist. For example, in one embodiment, the controlled-releasecomponent can swell and form porous openings large enough to release theactive ingredient after administration to a patient. The term“controlled-release component” in the context of the present inventionis defined herein as a compound or compounds, such as polymers, polymermatrices, gels, permeable membranes, liposomes and/or microspheres, thatfacilitate the controlled-release of the active ingredient (e.g.,S-tofisopam or salt thereof) in the pharmaceutical composition. Inanother embodiment, the controlled-release component is biodegradable,induced by exposure to the aqueous environment, pH, temperature, orenzymes in the body. In another embodiment, sol-gels can be used,wherein the active ingredient is incorporated into a sol-gel matrix thatis a solid at room temperature. This matrix is implanted into a patient,preferably a mammal, having a body temperature high enough to induce gelformation of the sol-gel matrix, thereby releasing the active ingredientinto the patient.

Pharmaceutical stabilizers can also be used to stabilize compositionscontaining S-tofisopam or prodrug or salts thereof; acceptablestabilizers include but are not limited to L-cysteine hydrochloride,glycine hydrochloride, malic acid, sodium metabisulfite, citric acid,tartaric acid and L-cysteine dihydrochloride.

Dosage forms according to the invention include tablets, coated tablets,caplets, capsules (e.g., hard gelatin capsules), troches, dragées,dispersions, suspensions, solutions, patches, pills, coated pills, andthe like, including sustained release formulations well known in theart. See, e.g. Introduction to Pharmaceutical Dosage Forms, 1985, Ansel,H. C., Lea and Febiger, Philadelphia, Pa.; Remington's PharmaceuticalSciences, 1995, Mack Publ. Co., Easton, Pa. For example, compositions ofthe present invention suitable for oral administration can be presentedas discrete units such as soft gelatin capsules, cachets, tablets,pills, or aerosol sprays, each containing a predetermined amount of theactive ingredient. Alternatively, compositions of the present inventioncan be in the form of a powder or granules or as a solution or asuspension in an aqueous liquid, a non-aqueous liquid, an oil-in-wateremulsion, or a water-in-oil liquid emulsion. Such compositions can beprepared by any of the methods of pharmacy but all methods include thestep of bringing into association the active ingredient with thecarrier. A preferred solid oral preparation is tablets. A more preferredsolid oral preparation is coated tablets. If desired, tablets can becoated by standard aqueous or nonaqueous techniques.

In general, the compositions can be prepared by uniformly and intimatelyadmixing the active ingredient or prodrug with liquid carriers or finelydivided solid carriers or both, and then, if necessary, shaping theproduct into the desired presentation. For example, a tablet can beprepared by compression or molding, optionally with one or moreaccessory ingredients. Compressed tablets can be prepared by compressingin a suitable machine the active ingredient in a free-flowing form suchas powder or granules, optionally mixed with one or more of a binder,filler, stabilizer, lubricant, inert diluent, and/or surface active ordispersing agent. Molded tablets can be made by molding in a suitablemachine a mixture of the powdered compound moistened with an inertliquid diluent.

In one embodiment, each tablet contains from approximately 10 mg toapproximately 100 mg of the active ingredient or prodrug, and eachcachet or capsule contains from approximately 10 mg to approximately 300mg of the active ingredient or prodrug. In another embodiment, thetablet, cachet or capsule contains one of four dosages: approximately 10mg, approximately 50 mg, approximately 100 mg, and approximately 150 mgof active ingredient or prodrug.

In the case where the composition comprises an anticonvulsant other thanS-tofisopam, salt or prodrug thereof, the other anticonvulsant can bepresent in an amount less than, greater than, or equal to the amount ofS-tofisopam, salt or prodrug thereof, as physically allowed by thepharmaceutical arts.

In a preferred embodiment, the subject to be treated according to themethods of the invention is a mammal. In another preferred embodiment,the subject to be treated according to the methods of this invention isa human.

Convulsions according to this invention are involuntary musclecontractions caused by abnormal neuronal activity resulting incontortion of the body and/or limbs. Seizures according to thisinvention are transient changes of behavior induced by the disordered,synchronous and rhythmic firing of neurons. Periodic unpredictableoccurrences of seizures are commonly associated with epilepsy. The twomain types of epileptic seizures are partial seizures and generalizedseizures. Partial seizures as used herein, are characterized as thosethat affect neurons limited to part of one cerebral hemisphere. Partialseizures can or can not be accompanied by impairment of consciousness.Generalized seizures as used herein, include those in which bothhemispheres are involved and consciousness is usually impaired.Generalized seizures include absence seizures, myoclonic seizures,clonic seizures, tonic seizures, tonic-clonic seizures and atonicseizures (Dreifuss et al., Classification of Epileptic Seizures and theEpilepsies and Drugs of Choice for Their Treatment, p. 1–9, In:Antiepileptic Drugs: Pharmacology and Therapeutics, Eds M. J. Eadie andF. J. E. Vajda; Wilder et al., Classification of Epileptic Seizures, p.1–13, In: Seizure Disorders, A Pharmacological Approach to Treatment,Raven Press, New York (1981)).

Pseudoepileptic or non-epileptic seizures can be caused by a definablemedical cause, e.g., cardiovascular disease including arrhythmias,aortic stenosis, and orthostatic hypotension; toxic or metabolicdisorders including hypoglycemia and drug toxicity; or sleep disorders.Non-epileptic seizures can also be induced by psychiatric conditions,e.g., hysteria, schizophrenia.

Convulsions or seizures can result from disorders or specificconditions, e.g., epilepsy, acquired immunodeficiency syndrome (AIDS),Parkinson's disease, Alzheimer's disease, other neurodegenerativedisease including Huntington's chorea, schizophrenia, obsessivecompulsive disorders, tinnitus, neuralgia, trigeminal neuralgia,amyotrophic lateral sclerosis (ALS), tics (e.g., Gille de la Tourette'ssyndrome), post-traumatic epilepsy, alcohol use, alcohol withdrawal,intoxication or withdrawal from barbiturates, brain illness or injury,brain tumor, choking, drug abuse, electric shock, fever (especially inyoung children), head injury, heart disease, heat illness, high bloodpressure, meningitis, poisoning, stroke, toxemia of pregnancy, uremiarelated to kidney failure, venomous bites and stings, withdrawal frombenzodiazepines, febrile convulsions, and afebrile infantileconvulsions.

The magnitude of a prophylactic or therapeutic dose of the activeingredient (e.g., S-tofisopam or salt thereof) or S-tofisopam prodrugand, if desired, other anticonvulsant for treating or preventingconvulsions or seizures will vary with the severity of the patient'saffliction and the route of administration. The dose and dose frequencywill also vary according to the age, weight and response of theindividual patient. In general, the recommended daily dose range for theconditions described herein can lie within the range of fromapproximately 10 mg to approximately 1200 mg per day, generally dividedequally into doses given one to four times a day. A daily dose range canbe between 50 mg and 600 mg per day, usually divided equally into a oneto four times a day dosing. Alternatively, a daily dose range can bebetween 100 mg and 400 mg per day, usually divided equally into a two tofour times a day dosing. Also, when based on the body weight of thepatient, S-tofisopam may be administered at a dosage of less than 30mg/kg of the patient's body weight. It can be necessary to use dosagesoutside these ranges in some cases and adjust the amounts ofS-tofisopam, salt or prodrug thereof administered alone or incombination with the other anti-convulsant(s). The treating physicianwill know how to increase, decrease or interrupt treatment based uponpatient response. The various terms described above such as“therapeutically effective amount,” are encompassed by theabove-described dosage amounts and dose frequency schedule.

For use in treating or preventing convulsions or seizures, the physicianwill generally prescribe the period of treatment and frequency of doseof S-tofisopam, substantially free of R-tofisopam, on apatient-by-patient basis. In general, however, treatment or preventionof convulsions or seizures with S-tofisopam, prodrug or salt thereofsubstantially free of R-tofisopam, can be carried out for as long aperiod as necessary, either in a single, uninterrupted session or indiscrete sessions. For example, therapy can be carried out for a periodof 4 to 18 weeks.

According to the methods of this inventio, S-tofisopam, salt or prodrugthereof can be administered alone or in combination with one or moreother anti-convulsants to treat or prevent convulsions or seizuresincluding myoclonic jerks (i.e., clonic activity). The otheranti-convulsant can be selected from the group consisting of, ut is notlimited to, phenytoin, mephenytoin, ethotoin, phenobarbital,mephobarbital, primidone, carbamazepine, ethosuximide, methsuximide,phensuximide, valproic acid, trimethadione, paramethadione, phenacemide,acetazolamide, progabide, diazepam, lorazepam, clonazepam, clorazepateand nitrazepam. The other anti-convulsant can be included in thecomposition comprising S-tofisopam, salt or prodrug thereof.Alternatively, the other anti-convulsant can be administeredsimultaneously with the composition comprising S-tofisopam, salt orprodrug thereof, or at any time during the treatment of the subject withthe composition. According to one aspect of the invention, S-tofisopamis administered together with at least one other benzodiazepine to treator prevent convulsions or seizures. In another aspect of the invention,S-tofisopam is administered together with at least one other1,4-benzodiazepine. In yet another aspect of the invention, S-tofisopamis administered together with diazepam, lorazepam, clonazepam,clorazepate or nitrazepam to treat or prevent convulsions or seizures.

Any suitable route of administration may be employed for providing thesubject of this invention with an effective dosage of S-tofisopamsubstantially free of R-tofisopam. For example, oral, rectal,parenteral, transdermal, subcutaneous, sublingual, intranasal,intramuscular, intraperitoneal, intrathecal and the like can be employedas appropriate.

Throughout this specification, the word “comprise” or variations such as“comprises” or “comprising” will be understood to imply the inclusion ofa stated integer or group of integers but not the exclusion of any otherinteger or group of integers.

U.S. Provisional Application No. 60/292,026 filed May 8, 2001, is herebyincorporated by reference herein in its entirety.

The present invention is illustrated in the following examples. However,it should be noted that these examples are for illustrative purposesonly and are not to be construed as restricting the invention in anymanner.

EXAMPLE 1

Resolution of S-tofisopam

The enantiomers of tofisopam were resolved by chiral chromatography. Forexample, tofisopam (42.8 mg dissolved in acetonitrile) was loaded onto aChirobiotic V column (ASTEC, Whippany, N.J.). Elution of the compoundswith MTBE/ACN 90/10 (v/v), 40 ml/min, was monitored at 310 nm, 2 mmpath. The R(+) enantiomer was the first compound to elute from thecolumn. R(−) tofisopam (“A′”), S(+/+) tofisopam (“B” and “B′”), andresidual R(+) tofisopam (“A”) co-eluted and was collected in asubsequent fraction.

The S(−) enantiomer was isolated from fraction 2 by the followingprotocol. Fraction 2 was dried, re-dissolved in 1 ml of acetonitrile andloaded onto a Chirobiotic V column. Peak B and B′ was shave recycledover a Chirobiotic V column two more times (MTBE/ACN 90/10 (v/v), 40ml/min monitored at 310 nm, 2 mm path). A peak containing S(−) tofisopamwas collected from the third recycle, dried and stored for use inbiological assays.

The final preparations of R- and S-tofisopam were assayed forenantiomeric purity by two different groups. One group reported that thefinal preparation of R-tofisopam was 98% pure (i.e., enantiomeric excessof 96%), and that of S-tofisopam was 95% pure (i.e., enantiomeric excessof 90%). The second group reported that the R-tofisopam was greater than97.5% pure (i.e., enantiomeric excess of >95%), and that the S-tofisopamwas 87% pure (i.e., enantiomeric excess of 74%), as determined byanalytical chromatography. Analytical evaluations of the startingmaterial and final preparations of R- and S-tofisopam as performed bythe second group was carried out using Chiral Tech OD GH060 columns(Daicel) (hexane/IPA 90/10, 25° C., detection at 310 nm). We believethat the results of the analysis of the purity of R- and S-tofisopamobtained by the second group were correct. The second group was also thegroup that tested the enantiomeric purity of the R-and S-tofisopamobtained as described in Example 3 below.

EXAMPLE 2

Evaluation of Tofisopam and its Enantiomers as Anti-convulsants

Picrotoxin was used as the convulsing agent and diazepam, an establishedanti-convulsant, was used as a control. Anticonvulsant activity againstpicrotoxin-induced seizures is considered evidence of clinicalantiepileptic potential and reason for further evaluation of a testcompound's anticonvulsant profile (Swinyard, E. A. et al., Generalprinciples: experimental detection, quantification and evaluation ofanticonvulsants. In: Antiepileptic Drugs, D. M. Woodbury et al., eds.Raven Press, New York (1990) pp. 111–126).

Male NSA mice weighing approximately 20–25 g, were injectedintraperitonealy (i.p.) with various doses (8–10 animals/dose) ofdiazepam, tofisopam, R-tofisopam of Example 1, or S-tofisopam of Example1, 15 minutes prior to picrotoxin injection. Picrotoxin (5 mg/kg, SigmaChem. Co., St. Louis, Mo., USA) was dissolved in saline and administeredsubcutaneously to induce seizures. In addition, picrotoxin alone wasadministered to seven animals as a control. All test drugs weredissolved in dimethylsulfoxide (DMSO). Both S- and R-tofisopam displayeda yellow color when dissolved in DMSO.

After picrotoxin injection, mice were placed into a plexiglass cage for30 minutes of observation. The appearance of seizures was defined as thepresence of a single episode of clonic or tonic activity (includingmyoclonic jerks) during the 30 minute observation period. The drugvehicle DMSO did not have any effect on seizure activity at theconcentration used. Animals were euthanized immediately after theobservation period by CO₂ inhalation. The ED₅₀ (the dose of testcompound at which half of the animals were protected againstpicrotoxin-induced seizures) values and their 95% confidence limits werecalculated by the method of Litchfield and Wilcoxon (J. Pharmacol. Exp.Ther. 96:99–113 (1949)). Results of these experiments are summarized inTable 1 below.

The effect of tofisopam on picrotoxin-induced seizures in NSA mice isshown in FIG. 1. Racemic tofisopam produced a dose-dependent inhibition(expressed as percent protection) of picrotoxin-induced seizures in micewhen administered by the intraperitoneal route. The ED₅₀ (95% confidencelimits) value was 37.8 (28.2–50.8) mg/kg.

R-tofisopam did not inhibit picrotoxin-induced convulsions at either 20or 50 mg/kg. On the other hand, the (S) enantiomer exhibitedanti-convulsant activity with over 60% protection at 40 mg/kg. (see FIG.2). An estimate of the ED₅₀ (95% confidence limits) of S-tofisopam was35 (28–43) mg/kg.

TABLE 1 Summary of Anti-convulsant ED₅₀ Values for Compounds Tested ED₅₀(95% Compound Tested confidence limit) mg/kg diazepam 0.52 (0.24–1.08)tofisopam 37.8 (28.2–50.8) R-tofisopam Inactive S-tofisopam   35 (28–43)

These data indicate that both racemic and S-tofisopam have intrinsicanti-convulsant activity against picrotoxin-induced seizures in NSAmice. In contrast, the (R) enantiomer of tofisopam showed noanti-convulsant activity.

EXAMPLE 3

Preparation of Tofisopam Enantiomers

Tofisopam diastereomer salts were prepared using the followingprocedure. (1) 3.0 g of racemic tofisopam was first dissolved in 10 mlof chloroform, after which 10 ml of distilled water was added to thedissolved racemate (solution A). (2) In a separate container, 1.5 g ofD- or L-dibenzoyl-tartaric acid (DBTA) was dissolved in 20 ml chloroform(molar ratio of 0.56 of DBTA to tofisopam) (solution B). The mixture wasstirred and heated to 45° C. until dissolution was complete. DB-(L)-TA(characterized by negative optical rotation) was used to purifyR-tofisopam, whereas DB-(D)-TA (characterized by positive opticalrotation) was used to purify S-tofisopam. (3) Solutions A and B weremixed and stirred until precipitation was complete. The mixture was thencooled to 5° C. to enhance yield. The solids were filtered, washed threetimes with 4 ml of cold chloroform, and dried.

To dissociate the tofisopam diastereomer salts and recover the resolvedtofisopam, the dried material was (4) suspended in 50 ml of 0.5M NaOHand then stirred for 2 hours with 10 ml of chloroform. (5) The aqueousphase was separated away and discarded, and the chloroform layer wasevaporated to dryness. (6) The solids were then triturated with 50 ml of5% acetic acid until the gummy paste became granular. (7) The resultingsolids were filtered and dried. (8) The pH of the filtrate was raised byat least 10 by using solid sodium hydroxide pellets and stirring for onehour. The solids were then filtered and dried. Production of S-tofisopamwith an enantiomeric purity of 96% (i.e., enantiomeric excess of 92%)required four enrichment cycles of the resolution procedure, wherein thesolids obtained at the end of the above procedure were redissolved andsteps 1–8 were repeated.

The final preparation of R-tofisopam and S-tofisopam was 95.6% pure(i.e., enantiomeric excess of 91.2%) and 96% pure (i.e., enantiomericexcess of 92%), respectively, as determined by analyticalchromatography.

EXAMPLE 4

Evaluation of Tofisopam and its Enantiomers as Anit-convulsants

The preparations of the tofisopam enantiomers of Example 3, as well asracemic tofisopam and diazepam, were tested using the picrotoxin-inducedconvulsion assay as described in Example 2. Results of these experimentsare summarized in Table 2 below.

Racemic tofisopam produced a dose-dependent inhibition ofpicrotoxin-induced seizures in mice with an ED₅₀ (95% confidence limits)value of 51.4 (26.8–98.5) mg/kg (see FIG. 3). Diazepam also produced adose-dependent anticonvulsant activity with an ED₅₀ (95% confidencelimits) value of 0.45 (0.27–0.77) mg/kg (see FIG. 4).

The effect of R-tofisopam on picrotoxin-induced seizures in mice isshown in FIG. 5. Although R-tofisopam exhibits anticonvulsant activityat doses of 32 mg/kg and 64 mg/kg, no further increase in protection wasobserved at 90 mg/kg. In addition, at a dose of 128 mg/kg ofR-tofisopam, no protection against picrotoxin-induced seizures in micewas observed. The ED₅₀ value could not be calculated because none of thedoses produced at least 50% protection from picrotoxin-induced seizures,and also because of the inverted U-shape of the dose response curve(FIG. 5).

S-tofisopam exhibited a dose-dependent anticonvulsant activity with anED₅₀ (95% confidence limits) value of 15.1 (7.6–30.1) mg/kg (see FIG.6).

TABLE 2 Summary of Anti-convulsant ED₅₀ Values for Compounds Tested ED₅₀(95% Compound Tested confidence limit) mg/kg diazepam 0.45 (0.27–0.77)tofisopam 51.4 (26.8–98.5) R-tofisopam not calculable S-tofisopam 15.1(7.6–30.1)

These data indicate that both racemic and S-tofisopam have intrinsicanti-convulsant activity, thus, supporting the conclusions from thestudy described in Example 2. In addition, these results demonstratethat highly pure S-tofisopam displays significantly greateranti-convulsant activity than the racemate compound.

1. A pharmaceutical composition comprising a therapeutically effectiveamount of S-tofisopam, a prodrug or a pharmaceutically acceptable saltthereof, substantially free of its R enantiomer, and a pharmaceuticallyacceptable carrier, wherein the amount of S-tofisopam, prodrug, or apharmaceutically acceptable salt thereof is from 25 mg to 300 mg.
 2. Apharmaceutical composition comprising a therapeutically effective amountof S-tofisopam, a prodrug or pharmaceutically acceptable salt thereof,substantially free of its R enantiomer, and a pharmaceuticallyacceptable carrier, wherein the amount of S-tofisopam, prodrug, or apharmaceutically acceptable salt thereof is from 50 mg to 600mg.
 3. Thepharmaceutical composition according to claim 2, wherein the amount ofS-tofisopam, prodrug or pharmaceutically acceptable salt thereof is from100 mg to 400 mg.
 4. A method of administering to a subject in need apharmaceutical coniposition comprising a therapeutically effectiveamount of S-tofisopam, a prodrug or pharmaceutically acceptable saltthereof, substantially free of its R-enantiomer, with a pharmaceuticallyacceptable carrier, comprisng preparing the pharmaceutical compositioncomprising of S-tofisopam, pro-drug or pharmaceutically acceptable saltthereof and administering the pharmaceutical composition at a dose ofless than 30 mg/kg to said subject.